1. Field of the Invention
This invention relates to a parts mounting device wherein a suction and mounting nozzle performs a cycloid movement so that a high speed mounting of parts can be provided.
2. Description of the prior art
In one of conventional high-speed parts mounting apparatus, suction and mounting nozzles are mounted on an outer periphery of a rotating table to be vertically movable. Each nozzle is moved from a parts suction station to a parts mounting station with rotation of the rotating table. The rotating table is temporally stopped and each nozzle is lowered or raised at each station so that parts are sucked by the nozzles at the parts suction station and the parts are mounted on circuit substrates, for example, at the parts mounting station.
According to the above-described construction, the movement of the rotating table is intermittent and accordingly, the operation of each nozzle at each station is intermittent in a sequence of lowering, stop (suction or mounting), raising and stop (standby). The operation of the whole apparatus is thus intermittent, which is one of causes for interrupting the high-speed parts mounting work.
The assignees have jointly developed a parts mounting apparatus wherein the above-described intermittent movement of the apparatus has been changed to a continuous movement so that a high-speed mounting work can be performed. In the developed apparatus, suction and mounting nozzles are mounted on the outer periphery of a rotating carrier rotated in a horizontal direction so that the nozzles are turned in a vertical direction. With rotation of the rotating carrier, each nozzle is turned along the outer periphery of the carrier in the state that each nozzle is directed downward. In this construction, each nozzle performs a cycloid movement in the direction of the outer periphery of the rotating carrier with its rotation. The cycloid movement of each nozzle has a plurality of bottom dead points. A part is sucked in the distal end of the nozzle when the nozzle reaches predetermined one of the bottom dead points corresponding to a part sucking stage and the suction is released when the nozzle reaches another predetermined bottom dead point corresponding to a part mounting stage so that the part is mounted on the circuit substrate.
In the apparatus utilizing the cycloid movement, however, a mounting error and a dimensional error of the nozzle, an error in setting return to origin and the like cause errors in the position of the nozzle at part sucking and mounting points or the position of the nozzle when it reaches the bottom dead point in the cycloid movement. The part is not sucked by the nozzle or is improperly mounted on the substrate when the errors in the position of the nozzle at the part sucking and mounting points are increased. Accordingly, the errors need to be compensated so that the precision in the part sucking and mounting positions of the nozzle can be secured.
It has been proposed that the rotating carrier be stopped so that the positional errors of the nozzle at the bottom dead point are compensated, as in the same manner in the conventional parts mounting apparatus. However, in the apparatus utilizing the cycloid movement, a number of gears are employed in a transmission system for the cycloid movement of the nozzle. Consequently, even when the position of the nozzle is compensated in the state that the rotating carrier is stopped, the position of the nozzle is deviated during the operation from the compensated one by a cumulative error due to some play in the gears of the transmission system. Accordingly, it is difficult to precisely compensate the position of the nozzle at the bottom dead point in the state that the parts mounting apparatus is deenergized. The position of the nozzle at the bottom dead point during the cycloid movement needs to be precisely compensated.